Process of and apparatus for treating, dewatering, compressing, and drying industrial wastes, sewage solids, etc.



Oct, 26 1926.

F. W. MANNING PROCESS OF AND APPARATUS FOR TREATING DEWATERING,COMPRESSING,

AND DRYING INDUSTRIAL WASTES,SEWAGE SOLIDS, ETC

Filed June 1,7, 1925 4 Sheets-Sheet 1 INVENTOR. FREQ WMjfNNJNQ ATTRNEYIS'.

Oct. 26, 1926; N 1,604,652

' W. MANNING F. v PROCESS OF AND APPARATUS'FOR TREATING DEWATERING,COMPRESSING,

AND DRYING INDUSTR AL WASTES,SEWAGE SOLIDS, ETC

. Fil d-June 17, 41925 4 Sheets-Sheet 2 INVENTOR. FREQ WMEQNNJNG'I M m Mr ATTORNEYS F. w. MANNING PROCESS OF AND APPARATUS FOR TREATINGDEWATERING, COMPRESSING,

' AND DRYING INDUSTRIAL WASTES SEWAGE SOLIDS; ETC

- Filed June 14',- 1925 4 Sheets-Sheet 5 INVENTOR. FREQ WMJZNN/NG YQIIWrMZ-MW rQ- ATTORNEYS.

, ETC

4 Sheets-Sheet 4 MANNING F. W. PROCESS OF AND APPARATUS OR TREATINGDEWATERING, COMPRESSING,

Filed June 1 {K ,4 'IIIII.

Oct. 26- 1926.

AND DRYING INDUSTRIAL WASTES SEWAGE somns \I II. I

IINVENTOR. FJfEQ TM M ){NNING Patented Oct. 2 6 192d I UNITED STATESPATENT OFFICE.

FRED w, MANNING, on BERKELEY, CALIFORNIA,

PROCESS OF AND, APPARATUS FOR TREATING, DEWATERING, COMPRESSING, AND

DRYING INDUSTRIAL WASTES, SEWAGE SOLIDS, ETC.

Application filed June 17, 1925. Serial No. 31600.

This invention relates to certain new and useful improvements in methodsof and apparatus for the treatment of fluids by solids or solidsbyfiuids as the case may be 6 but more particularly it relates to thetreat: ment and separation of waste solids from their liquids, thedewatering of wet sludges, etc., and the compressing and drying ofsolids. I l v In my co-pending applications Serial Nos. 689,178, filedJanuary 28, 1924; 747 431, filed November 3,. 1924; and 20,155, filedApril 2, 1925, I have described 'how ,heavy granular solids such as'fullers earth and bone char, 1 etc, maybe introduced into liquidsSuch'as oil, and sugar solutions, and's'epara'ted therefrom. My presentinvention describes how liquids and sludges already containing finelydispersed solids or liquids which are difiicul to filter and clarify,such as the colloida and slimy materials contained in industrial wastes,by-products of sewage treatment plants, etc., may be treated, separatedfrom their liquids, compressed and dried. 1 My. (Jo-pending application,Serial No.

96,343, filed March 20th, 1926, describes certain improved continuousmethods whereby 'a granular treating agent such as fullers 4 1 earth,bone char, kieselguhr, etc., may be introduced in a dry powder stateinto a liquid under pressure and after one has been treatedcounter-currently by the other, the

agent removed from the liquid and dis-- charged from the apparatus in asimilar dry powdery state, and theseoperations accomplished without anyappreciable wear to the moving parts such as would be occasioned by theuse of flushing valves and collection or compression chambers.

It has been the practice "heretofore wherever continuous operatingapparatus could be used,'to accomplish the separating and preising, ofindustrial wastes, sewage solids, etc., by means of continuous screwpreses which exert heavy pressures but have very limited filteringareas, or bycontinuous suc tion filters which are usually not onlylimited as to filtering areas'but also limited as to temperatures andvery muchlimited as to pressures, and. the drying is accomplished in alseparate apparatus, usually rotary kilns. This arrangement requ1res anexcessive amount of fuel and especially is this so wherelarge amounts ofsludge are to be heated before filtering, as the heating of activatgdsludge for dewatering by rotary suction filters which reduce themoisture content seldom as low as 80% after which rotary kilns 7 furtherreduce themoisture content to approximately 10%. Even high pressures inthe case of such material as activated sludge will not reduce themoisture content to any appr 'iable extent'below 80% unless the'filterca re solids a're constantly turned over and over on the filter wall.The reason. for this is probably because in many colloidal materials thevery fine particles of liquid are completely surrounded with anagglomeration of very fine solid "particles which,

when subjected to high pressures, are simply jammed togetherafiording nooutlet for-the liquid particles and to afford such outlet the fineparticles of solids with entrained particles ofliquid must .beconstantly agitated "on the filter Wall under a filtering differentialpressure.

As is Well known to those versed in the art, the greatest filteringrates for the great majority of purposes are'obtained' by"filter.-

ing at high pressures either inwardly or outwardly through both sides ofthin filtering walls spaced as closely together in a given apparatus-aspossible, Unfortunately no practical method, as far as I am aware,

has ever been devisedfor 'doing this and removing the filter cake solidscontinuously. It is therefore an object of my invention to obtaingreatly increased capacities by com- ,bining the advantages of highfiltering pressuresand maximum filtering areas, and by means of scraperarms carrledon an endless chaln, coacting with flights of filter orcounter current screws, continuously move the filtered solids forwardinto and through a compression chamber where the moisture content islowered beyond that which is'usually obtained, and then into asucceeding section of the same apparatus where the solids arereconditioned or dried by the passage of fluids through the solids insimilar" manner, and without loss of content values, as, for example,nitrogen, ivhere the solids are to be finally used its/fertilizers. 4 Itis a further object of my invention to treat a liquid or a sludge inonechamber by two difi'erent'treating agents as by a coagulating or adecolorizing agent and a clarify- 1 ing agent and to keep the clarifyingagent separate from the sludge solids or liguid impurities and othertreating agent during the bestos, paper treating and clarifyingoperations and final- 1y to discharge them from the chamber separatelyso that the clarifying agent may be revivificd and used over again.

It is a still further object of my invention to constantly agitatematerial of a colloidal nature while gathered on a filter wall andsubjected to a differential filtering pressure. In accordance with myinvention I introduce aliquid or sludge to be treatedand from which anycontained solids or impurities are to be eliminated, into one end of thefirst section of an apparatus and force it toward the oppositeendthrough the counter current flights of a screw as described in myco-pending application, Serial No. 747,431, through a middle chamberbetween thecounter current and filter chambers, where the treating orconditioning agents areintroduced by means of a suitable feeding valve,and into a filter chamber'where the liquid passes upward or forward andcompletely surrounds another screw, both sides of which are equippedwith filter walls and through which the liquid passes as a perfectlyclarified filtrate into andthrough'and out of the hollow filter screwshaft, the elimination of the sludge solids or liquid impurities beinggradual during the entire forward movement of the liquid or sludgethrough the counter current flights.

Treating solids such as lime, aluminum sulfate, etc., for thecoagulation or flocculation of the colloidal matter or for otherpurposes and clarifying solids such as kieselguhr, aspulp, etc., forclarifying purposes, are fed into the chamber, the treating agent justbelow the last one or two counter current flights which prevents itsmovement into the middle chamber and which co-operating with the scraperarms on an endless chain moves the treating solids downward or forwardin one direction while the sludge solids or liquid impurities buildthereupon or are agitated with it and the liquid filters therethrough inits counter current movement until the solids finally pass through thecompression chamber and are discharged into the next section of'thevapparat-us. The clarifying agent entering the middle chamber is carriedupward or forward in another direction by the movement of the liquid andcompletely surrounds and builds upon the walls of thefilter flights,

the greater portion building upon the first flight where the filter cakestarts on its for-v ward movement to a collection or compres sionchamber from which it is discharged in similar manner to the treatingagent and sludge solids or liquid impurities at the opposite end of thesection.

be counter current and filter screws may be of the same hand and rotatein opposite directions, or they may be of opposite hands and rotate inthe samedirection. The move rections, the clarifying agent toward oneexit'and the treating agent with the sludge solids or liquid impuritiestoward the opposite exit. In this way the clarifying agent may be keptpracticallv' free from the sludge solids or liquid impurities and usedsimply for removing the finest colloidal matter bacteria, etc., andafter being discharged may.

be revivified and used over again.

The'solids from either end of the first section of the apparatus uponentering the second section are conveyed therethrough in similar mannerby the co-action of a rotating screw and scraper arms on an endlesschain and in counter direction to a reconditioning or drying fluid whichenters under pressure at the opposite end of the section, and advancingthrough the counter current fli hts against the forward movement of theso ids finally escapes through the filter flights carried on the upperend of the counter current shaft. The solids after being reconditioned,or dried or calcined as by a wash liquid, compressed air, saturated orsuperheated steam, heated furnace gases or other suitable fluids, passthrough a collection orcompression chamber of similar design to thesolid exit of the previous. section, or they may be passed out of thecounter current chamber by means of a discharging valve of similardesign to the feeding valve. The solids may section of the apparatus ofsimilar design to the second section for further reconditioningpurposes.

Throughout this specification and the appended claims the term treatingsolids intended to define any agent brought into contact by thedescribed method with either liquid or gas for the purpose offlogculation or coagulation or for other purposes such as absorption,adsorption, revivification, difi'u sion, extraction, catalysis,precipitation of solids from liquids, water softening by means ofexchange silicates, or for any solids used simply as a filter aid tospeed up the rate of filtration and to keep the filter wall clean. v

The features of the invention hereinbeforc referred to in general termswill bebetter understood by reference to the following description takenin conjunction with the accompanying drawings, which illustrate apractical embodiment of the invention. 'It will be'understood,however,that the construction herein illustrated and described is merelyillustrative of how the features of .the invention may be employed. andthat the invention is not limited as to structural teathen be passedinto a third tures except as may be indicated by the terms employed inthe claims appended hereto.

The invention will now be more specifically described by reference tothe accompanying drawings wherein- Fig. 1 is a side elevation of thefirst section of one form of apparatus for practicing my invention. 1

Fig. 5 is a horizontal sectional view area on line 5- 5 of Fig. 4.-

Fig. 6 is a front elevation of the discharging door shown in Fig. 4.

Fig. 7 's a. horizontal sectional view taken I on line 7-7 of Fig. 3.

Fig. 8 is. a modified part view of Fig. 7 showing a method of supportingthe scraper arms. c

Fig. 9 is a sectional elevation of one of the filter flights, Y

Fig. 10 is a. plan view of one of the counter current flights. i

Fig. 11 is a sectional elevation of one of the counter. current flights.1

Fig. 1 illustrates the first; section of the apparatus complete,comprising feeding valve V, filter chamber F,'middle chamber M, countercurrent chamber (I -C,v top and bottom compression chambers C and Crespectively and pump P. i

Fig. 2 illustrates the second or a succeedin section of the. apparatusand how the so ids from the lower end of the preceding section may bedischarged into hopper H, and by means of feeding valve '0 passed intofilter chamber F or the solids may be conveyed directly into the filterchamher 'from the compression chamber of the previous section 'as'.shown in Fig. 6 of my co-pending application Serial No. 747,431, andafter passing through the filter chamber F and counter current chamberC'-C?pass out of collectiorror compression chamber C. If it is desirableto wash the solids before drying, this second section will ordinarily bea duplicate of the first section in which case the solids will be fedinto the counter current chamberin the same manner as the treatingsolids in the first section. The section as shown inFig.

2 differs mainly from the 'se'ctiomshown in Fig. 1 in that the filterflights and counter current flights are mountedon one shaft and and aredriven from above andthe solids allmove in one direction.

In the first section, the filter flights 1 are keyed to hollow shaft 7driven from above, and the counter, current-flights 3 and 5. to

hollow shaft 9 driven from below. Valve 11 is attached to valve stem 13operated byhand wheel15 and isfor'th e purpose of allowing cloudyfiltrate from the filter chamber to be discharged through the countercur-- rent shaft. A chamber 17 completely enclosed except on sideadjacent to tank shell 19, serves as'aguide for the return. movementofthe scraper arms. 21 which movement is actuated by rotation of thecounter ourrent flights 3 and 5. These arms are connected intoan'endl'ess chain by means of' links 23 passing over pulleys 25 and 27.An

upper guide chamber 26 encloses the chain of scraper arms forcooperating with the filter flights 1 and is slightly offset from theguide chamber 17 as shown in Fig. 7

so as to enable the scraper arms of each chain to clear each other inthe middle chamber. Both guide chambers form pockets into thecompression chambers C and C as shown at 30 so as to prevent sludge fromI being squeezed into the. guide chambers.

Division wall 32 prevents any liquid in the guide chamber fromshort-circuiting to the middle chamber without passing through thecounter current flights. .Usually the scraper arms will be subjected tovery little lateral pressure except in the compression chambers wherethe needed support is obtained by the compression chamber walls 22 and22 However, in cases where very heavy cake solids are being handled andsupportis re-' quired: for the ends of the scraper arms, it can beobtained by projecting the arms until they find a bearing against thehubs of the flights as shownin Fig. 8, the arrow head showing'thedirection of rotation. 1 4

The filter flights 1 areslightly smaller in diameter than the insidediameter of the shell-19"so as -.to permit the flow of fluids aroundthem and are-equipped on both sides with filtering fabric 29 and coveredwith thin perforated wearing plates 31. The

drainage spaces under the filter fabric are connected as shown with thehub annular chamber 34 which leads into hollow shaft 7 throughopenings33. The counter current ing plates as in the case of the filterflights, hutat any rate the filtering fabric should extend beyond thecircumference of the flights and bear against the cylindrical wall 19 sothat all the liquid will be compelled to: pass through the flights. Anarrow strip of braided wire tape clamped under the ring 35 and bearingagainst the wall as shown in not be protected with'thin perforated wear-Fig.v 11 would serve the same purpose.---

Drainage channels 37 and small holes 39 permit the fluid to pass throughthe flights in a thoroughly dispersed and uniform movement.

The compression flights may also serve as counter current flights and beequipped in the same way. However, if very heavy pressure is required,the compression chamber may be equipped with a cylindrical cage of heavyfilter bars in the well known way common to most continuous screwpresses in which case the filtrate after passing through the filterbars, could be pumped back through feed inlet 43 or led to the run downtank T, the purpose of which is described later on. The annular space inthe com, pression chamber between two of the flights is always filledwith a ring of solids which relieves the discharge door 41 of anconsiderable pressure. This ring of soli s also prevents any liquidescape through the discharge door in cases where the regular forwardmovement of solids from within fail. The hubs of the co mpression screwflights 5 may betapered as indicated in Fig. 4, so as to compress thesolids just previous to their exit from the first section but thisordinarily would not be required during the discharge of the clarifyingsolids or in succeeding sections of the apparatus, in which cases thesechambers will be considered simply as collection chambers. Bearings 42,44and 46 take the radial and end thrusts of the counter currentandfilter shafts in the first section and bearings 48 and 50 the radial andend thrusts of the shaft in the second section.

The operation of the apparatus thus con structed has been in partindicated in a foregoing description. Sludge to be dewatered andcompressed or liquid from which impurities are to be removed, enters at43, passes up through the counter current flights, the lower ones ofwhich may be equipped with coarser screens or filtering fabric thanthose above, the last flight next the middle chamber being equipped withthe finest of all. The finest mesh of these graded filtering fabricsnaturally receives the lightest or least impervious filter cakes as thesludge solids or liquid impurities have been gradually eliminated by thetime the liquid reaches the middle chamber and consequently, despite thefineness of the filtering mesh, as good a rate of flow is obtained asnear the sludge inlet where the filtering mesh is much coarser. Duringthe upward or forward movement, the liquid with solid contents comes incontact with coagulating or other treating solids moving downwards or inthe opposite direction which enter from the feeding valve V, throu hentrance 45 situated one or two flights elow the middle chamber. Thesetreating solids are usually of granular'form and ordinarily tend toincrease the rates of filtration rather'than real-d it- The 'liquid, onpassing through the last low end. of shaft 8 and outlet 53.

counter current flight enters the middle =chamber M comparatively freefrom all solids and is then mixed with a clarifying agent entering fromfeeding} valve through entrance 47. The liquid with clarifying agentfreely passes upward or forward and surrounds the filter flights, butthe greater portion of the entering solids gather upon the first flightwhere the cake begins to build resulting in a cloudy filtrate which isdrained downwardly through the countercurrent shaft and discharged intorundown tank T from which it is withdrawn by pump P to flush thetreating and clarifying solids thru the feeding valve into the'chamberM, the clear filtrate resulting from the remain der of the filterflights being carried out through the hollow filter shaft 7 anddischarged from pipe 55. The filter cake solids, after forming on thefilter walls of both sides, of the first filter flight is moved alongover the other filter flights and finally through the collectionor'compression chamber from which it is discharged to be revivified andused over again.

The sludge solids or, liquid impurities wither without treating solids,on passing through and out of the compression chamber C are dischargedinto a hopper .H and through a feeding valve V and entrance 49 into thesecond section of the apparatus.

They" are then advanced in a similar manner to that of the firstsection, first by the filter flights 1 and then by the counter cur-v ina t oroughly dispersed condition and under pressure, will result in arapid and uniform treatment of the solids and the. continuous movementof the scraper arms through a water bath in the b0t't0m of guide chamber17 will prevent their overheating when hot" gases are used. A suitableinlet 65 and outlet 67 will maintain the cooling Water at the levelshown. Compressed air, saturated or. superheated steam, hot furnace orother kindsof gases which may be oxidizing, neutral or reducing fordrying, activating,- revivifying or for other purposes, enter at 51' andleave the filter chamber F through the filter flights, 1 hnll- T e beingdischarged clarifyi solids, after from-col action or compression chamberQ of the first section, may also be treated in It will also be seen thattwo solids may be a similar manner. v

The filter and counter current flights in the second section, beingmounted on the same shaft must needs rotate at the same speed, but inthe first section the filter flights, will ordinarily rotate at a muchslower speed thus causing the clarifying solids to move through thefilter chamber very slowly.- When desirable the rotation of the filterflights may be intermittent and the counter current flights continuousunder which condition, during the coating of the filter flights withclarifyin solids, the entire filtrate from the filter c amber will becloudy and be discharged through counter current shaft to the run downtank T by theogening of'valve 11 by hand wheel '15and t coating has beenaccomplished and the filtrate has obtained the desired clarity, gatevalve 59 controllingrthe discharge of the clarifying solids to thefeedin valve V is closed and the filtrate is turne back to its normalcourse and discharge through filtrate outlet by the opening of valve 57and the closing of valve 11. At the end of the filtering period valve 57is again closed and by means of mechanism, not shown, gear 63 is throwninto gear with lts motive power and the clarifying solids aredischarged, after which the rotation of the filter flights is stopped,gate valve 59 is opened and the coating of the filter flights isrepeated. Or if desired the precoating may be removed only at longintervals of time by so arranging that additional clarify-' ing solidsare continuously introduced into the middle chamber and moved over theprecoating until such precoating requires to be rep aced which may thenbe accomplished in a few minutes by reversing the flow of the filtratethrough the flights in conjunction with the rotation of the flights, inwhich case arrangements could be made to allow;

the incoming filtrate to escape through the first filter flight and thecloudy liquor out-- let into tank T.

It will thus be seen that the present invention provides a new methodand apparav tus whereby waste solids, colloidal or finely dispersedmaterial, solidor liquid, or impurities of any kind contained in afluid, or

any plastic material, may be gradually eliminated with the aid ofsuitable treating solids by means of counter current movements of thefluids and solids and that during the process of elimination, suchmaterials may be kept almost entirely segregated from a clarifying agentintroduced into the same chamber to-retain the finely dispersedparticles still contained in the liquid-or-fluidafter passing throughthe last counter current flight.

e closing of valve 57. After the continuously introduced for differentpurposes into a llquid 'or sludge in an enclosed chamber, and that onemay be used to adsorb or coagulate the impurities in the liquid.

or otherwise treat the liquidwcountercurrently, and'the other solid maybe used to clarify the treated liquid, and that either or the filterflights, the solids or impurities contained in the liquid being allowedto build on top of either or both precoatings and at the same time thatall thesolids are advancing continuously at a predetermined rate towardtheir respective outlets, or one solid may be advancing continuously andthe other intermittently toward their respective outlets. But whetherthe liquid or sludge solids. build upon the treatingand clarifyingsolids, or pass through them," or pass into and be retained by them,'-qrare constantly agitated with them by the movement of the lights coactingwith the scraper arms, depends upon the nature of theliquid or sludge,the amount of solid particles contained therein, the amount and purposeof the treating and clarifying agents introduced, and the pressure used.

It will also be evident that solids may be I treated with gases or gaseswith solids, countercurrently and under pressure and at anypredetermined rate of speed and that the invention is of more or lessgeneral application wherever solids, liquids, or gases are broughttogether for any purpose whatsoever and that variations may be made inthe details of the process and apparatus without departing from thespirit of the invention. 1

The counter-current treatment of gases or vapors and solids,particularly the continuous counter-current catalytic treatment ofcracked distillates in the vapor phase, is

described in my co-pending' application,

Serial No. 128,900, filed August 12th, 1926.

Having thus described my invention what I claim and desire to secure byLetters Patcut is--- 1. A filtering rocess consisting ofbuildingfiltered soli s upon a spiral filter wall between such wall and theliquid to be fil-* tered, passing theliquid through th'e'filtered solidsand filter wall, and moving the filtered solids along the wall.

2. A filtering process consisting of pre- I coating a filter wall,filtering therethrough and building the filtered solids upon theprecoating, and moving the filtered solids over the precoating. i

3. A filtering process consisting of-precoating a filter wall withclarifying solids and moving an additional clarifying or other treatingagent over said precoatmg.

a. A treating and filtering process consist- .ing of introducing aplurality of treating solids into a chamber containing a liquid,treating the liquid by passing certain of the solids through the liquid,and thereafter clarifying or otherwise further treating the liquid bypassing the liquid through other of the said solids, whilst the firstand second mentioned solids are moving through the said chamber indifferent directions.

' the liquid therethrough.

6. The process of treating and filtering sludge solids consisting ofintroducing the same into an enclosed chamber, supplying treating solidsthereto, moving the liquid in one direction through the chamber, movingthe treating and sludge solids in a counter direction, providingclarifying solids to the resultant filtrate in the chamber and movingthe clarifying solids through another portion of the chamber whilefiltering the liquid therethrough.

7. The process of treating and filtering sludge solids consisting ofintroducing the same into anenclosed chamber, supplying treating solidsthereto, moving the liquid in one direction through the chamber, movingthe treating and sludge solids in a counter direction, providingclarifying solids to the resultant filtrate in the chamber adjacent thetreating solids entrance'thereof, and moving the clarifying solidsthrough another portion of thechamber in a different direction to themovement of the treating solids while filtering the liquid therethrough.

8. A continuous process oftreatin and filtering sludge solids consistingof introducing the same into an enclosed chamber, supplying treatingsolids thereto, moving the liquid in one direction through the chamber,moving the treating and sludge solids in a counter direction collectingthe solids to expel the liquid therefrom, moving the collected solidsinto and through a second'chamber, and forcing drying gases through thesolids in the second chamber counter to the movement of the solids.

9. A continuous treating and filtering apparatus comprising an enclosedchamber, means for supplying a sludge and clarifying solids to differentportions of the chamber and means in the chamber for moving the sludgesolids and clarifying solids in different directions therethrough andfor separating the solids from the liquid.

10. A continuous treating and filtering flights in different parts ofthe chamber adapted by their rotation to move solids toward theirrespective ends of .the chamber and means adjacentlto the conjunction ofthe two said sets for forcing treating solids into the chamber.

12. A continuous treating and filtering apparatus comprising an enclosedchamber, means for forcing a sludge into the chamber adjacent one endthereof, two sets of screw flights in different parts of the chamberadapted by their rotation to move solids toward their respectiveends ofthe chamber and means adjacent to the conjunction of the two said setsfor forcing treating solids into the chamber, the flights of one saidscrew set being perforated to permit the filtering of liquidtherethrough' and the other set having the flights thereof formed into afilter wall in communication with an axial draining-duct in .the screwshaft.

13. The combination of an enclosed chamber, a screw therein having aplurality of flights, a plurality of scrapers each adapted to engage thescrew between two adjacent flights and a housing, .said housing andchamber completely enclosing the scrapers and screw, the screw beingadapted to rotate relatively to the scrapers.

14. The combination of an enclosed chamber, a screw therein having aplurality of flights, a plurality of scrapers mounted on an endlesschain and each adapted to engage the screw between two adjacent flightsand a housing, said housing and chamber completely enclosing thescrapers and screw, the screw being adapted to rotate relativelyto thescrapers.

15.- In an enclosed treating or filtering apparatus, a chambercontaining a plurality of filter elei nents connected together as onecontinuous spiral, and an endless chain of scraper armswhich coact withthe said filter elements. Y

16. A filter screw comprising a center shaft, a filter spiralcontinuously connected thereto, and means providing a filter wall alonga side of the spiral in communication 17. A filter screw comprising acenter shaft, a continuous spiral connected thereto along the length ofthespiral, and means 7 providing a filter wall on a side of the spiralin communication with a duct extending axially through the shaft.

18.1A filter screw comprising a center shaft, a filter spiralcontinuously connected thereto, and means providing filter walls on bothsides of the spiral incomniunication a duct extending axially throughthe s a t.

19. A filterfscr'ew comprising a center shaft, a continuous spiralconnected thereto along the length of the spiral, and means providingfilter walls on both sides of the spiral in communication with a ductex- 20 tending axially through the shaft.

FRED.- W. MANNING.

